The germination of fungal spores may be used as a convenient experimental system for study of mitochondrial biogenesis and for examination of the cooperation between the nuclear and mitochondrial genetic systems for organization of the mitochondrial respiratory membrane. Ungerminated, dormant spores of the mycelial fungus Botryodiplodia theobromae contain mitochondria which do not have the well-developed respiratory system of rapidly growing spores; they specifically lack cytochrome a, heme a, cytochrome c oxidase activity, and one of the two cytochromes b. The general objective of this proposed project is to study the respective biochemical contributions of the nuclear genetic system and the rudimentary, semi-autonomous genetic system of the mitochondria in the assembly and function of these organelles as the fungal spores undergo highly synchronized germination. The timing of synthesis of subunits of cytochrome c oxidase will be studied by immunoprecipitation and dodecylsulfate gel electrophoresis to determine which of the enzyme subunits are stored in the dormant spore and which of them are synthesized early in germination to permit the elaboration of cytochrome c oxidase activity. Experiments will be performed to establish whether synthesis of certain of the enzyme structural proteins is required in order for the cycloheximide-sensitive elaboration of cytochrome c oxidase to occur. Analogous biosynthesis studies will be performed to measure immunochemically the biosynthesis of ATPase during spore germination. In addition, the polyadenylated RNA of dormant and germinated spores will be translated in vitro to establish whether the mRNA of dormant spores codes for subunit polypeptides of certain enzymes of the mitochondrial respiratory system.